223/556 ammo question

[Bushwack44]

I'm sure there are variables in providing an answer. But let's give this a try.

Using an AR-15 with an 18" barrel....

My objective is, using factory ammo (for target shooting), will 2.23 or 5.56 be the better round for grouping at 200 or 300 yards? Also, between 55gr and 62gr, which would be better?

I'm not concerned about pricing. As I'm about to re-stock the 'compound' with ammo, I want to make (the right) bulk purchase to meet the objective. In the past I'd use Wolf in 2.23/55gr shooting steel at 200 & 300 yrds. Works well but I want to start shooting paper at 200 & 300 yrds and I was curious if there's a significantly better option going to 5.56 and/or 62gr.

[highpower790]

223 &556 are essentially the same.Dont expect any big differences.As for prescribing what ammo to use ,its going to be a trial and error issue.
What twist rate is the barrel?

[Divernhunter]

The twist rate of the barrel and the bullet in the ammo are the most important things and you did not let us know what you have. A 1-12" or 1-14" twist will mean you need to use 40-55gr lead core bullets or 36gr non-lead Barnes VG bullets.

[Bushwack44]

The twist rate of the barrel and the bullet in the ammo are the most important things and you did not let us know what you have. A 1-12" or 1-14" twist will mean you need to use 40-55gr lead core bullets or 36gr non-lead Barnes VG bullets.

Twist is 1:8.

[baih777]

Twist is 1:8.

Try different brands of 55gr.

[polygunner]

Buy as many different types of ammo you can find, 20rd boxes.

Find which one your rifle likes the best by shooting the ammo.

Buy as much of the best shooting ammo you can afford.

pg

[LynnJr]

223 is mainly commercial and 556 is mainly military so in general 223 ammo is more accurate.
Avoid FMJ military ammo if your after accuracy.
Military ammo is meant to produce a field of fire not win Benchrest matches so avoid it like the plague.
On your bullet weight question heavy bullets generally but not always have a better BC so they fight the wind better and are preferred as the distance is increased.
At 100 200 yards they won't show any increase in accuracy. It is only when you exceed 400 yards that they offer you any improvement and depending on the velocity that isn't always true either.
Since this is the reloading forum use commercial ammo or brass and a good 52-53 grain bullet and the 223 will do what you want.
For distances over 500 yards go to a 6mm and never look back.